Aqueous solution lubricant for aluminum cold rolling

ABSTRACT

Compositions related to a water-based lubricant fluid for aluminum cold rolling which is free from measurable particles or oil droplets which can be applied in field production. A single-phase lubricant fluid may include water-soluble polymers, lubricating additives, anti-rust additives, anti-oxidant additives, pH-adjust additives, or combinations thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit from U.S. Provisional PatentApplication No. 61/580,799, filed on Dec. 28, 2011, which isincorporated by reference in its entirety.

BACKGROUND

Aluminum cold rolling is one of the most important processes of aluminumapplication. The lubricant is critical for continuous production andgood quality. Traditionally, there have been two primary types oflubricating methods for the cold rolling processes: 1) lubrication withneat oils and 2) lubrication with oil-in-water emulsions. The firstgeneration lubricant is neat oil. Neat oil products provide good sheetsurface quality but also have critical defects: 1) easily combustible;and 2) higher rates of consumption. The second generation product isoil-in-water emulsion products. Compared with neat oil, emulsions avoidthe issues presented by the use of neat oil products. Potentialshortcomings of the emulsions include: 1) limited strip cleanlinessafter anneal as a result of too high evaporation temperature; and 2)ease in emulsification of tramp oil, which decreases rollingperformance.

U.S. Pat. No. 4,828,737 discloses the use of aqueous products inaluminum cold rolling. However, according to that patent, these aqueousproducts require a temperature of 360° C. before they evaporate. Theaqueous solution lubricants of embodiments of the present invention maybe completely evaporated at 240° C., thereby allowing all processconditions that are applied when (partially) annealing aluminum alloys.

The aqueous solution lubricant for aluminum cold rolling of someembodiments of the present invention has addressed the shortcomings oftraditional lubrication.

SUMMARY OF THE INVENTION

According to some embodiments, a lubricant fluid for aluminum coldrolling includes a single-phase water-based solution with a watersoluble polymer. In some embodiments, the polymer includes at least onehydrophilic group, such as ethylene oxide. In some embodiments, thepolymer's molecular weight is about 200 or greater. In certainembodiments, the lubricant fluid includes about 5 wt % to about 99 wt %water soluble polymer. In some embodiments, the lubricant fluid includesat least one lubricant additive, which may be water soluble. In someembodiments, the lubricant additive includes one or more carbon chainstructures, one or more hydrophilic groups, or a combination thereof. Alubricant fluid may include about 0.1 wt % to about 10.0 wt % lubricantadditive. In certain embodiments, the lubricant fluid includes at leastone functional additive, such as anti-rust additives, anti-oxidantadditives, pH-adjust additives, or combinations thereof. The lubricantfluid may include about 0.05 wt % to about 5 wt % functional additive.

DESCRIPTION OF THE FIGURES

FIG. 1 shows evaporation of lubricant fluids at different temperatures.

FIG. 2 shows a rolled strip with a reference formulation.

FIG. 3 shows a rolled strip with a formulation of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Compositions and methods of some embodiments of the present inventionrelate to aluminum cold rolling processes with single-phase water-basedlubricant fluids. Compositions and methods of the present invention mayinclude a water-based lubricant fluid for aluminum cold rolling which isfree or substantially free from measurable particles or oil droplets. Insome embodiments, a lubricant fluid includes one or more water-solublepolymers. A lubricant fluid may also include one or more of lubricantadditives, and various functional additives.

Traditionally, oil-in-water emulsions are applied to the strip duringaluminum cold rolling. However, use of oil-in-water emulsions may havedisadvantages, such as limited strip cleanliness after anneal,insufficient filterability, fluctuating emulsion characteristics leadingto inconsistency on the mill, high oil consumption, etc. In someembodiments, such disadvantages may be avoided by use of a single-phasedwater-based lubricant fluid according to some embodiments of the presentinvention. Single-phased water-based lubricant fluids according to someembodiments of the present invention may be useful for application incold rolling of any type of aluminum and alloy.

According to the traditional lubrication theory of cold rolling andindustry experience, two regimes of lubrication exist in the rollingprocess: boundary lubrication and elastic-hydrodynamic lubrication(“EHD”). Many aluminum rolling processes may be conducted in the mixedlubrication regime, including characteristics of both boundarylubrication and EHD lubrication. Therefore, in some embodiments,lubricant fluids of the present invention may providelubrication-boundary lubrication and/or elastic-hydrodynamiclubrication. Due to aluminum deformation stress, lubrication is inclinedto boundary lubrication. In some embodiments, lubricant fluids of thepresent invention may provide the following characteristics: 1) providegood surface quality with no obvious water-stain impression; 2) show noresidue on aluminum sheet after annealing, where all materials should beeliminated before 240° C.; and 3) reject tramp oil, which should beeasily separated from the solution.

Therefore, in some embodiments of the present invention, single-phasedwater-based lubricant fluids may provide sufficient lubricationproperties in boundary lubrication for use in cold rolling processes.

Lubricant Fluid Composition

In some embodiments, a lubricant fluid of the present invention includesa single-phase water based lubricant fluid. In some embodiments, asingle-phase water based lubricant fluid may include a water solublepolymer and optionally one or more lubricant additives, and variousfunctional additives.

Water Soluble Polymer

A lubricant fluid of the present invention may include one or more watersoluble polymers. In some embodiments, the polymers may be dissolved ordispersed in a volume of water.

In some embodiments, a suitable water soluble polymer includes one ormore hydrophilic groups. Examples of suitable hydrophilic groups includebut are not limited to ethylene oxide, propylene oxide, hydroxyl,carboxyl, acyl-amine and combinations thereof. In some embodiments, theevaporation temperature of these polymers is such that the final productis completely evaporated at temperatures less than 240° C.

In some embodiments, a lubricant fluid includes one or more watersoluble polymers in an amount of about 5 wt % to about 99 wt %; 10 wt %to about 95 wt %; about 15 wt % to about 90 wt %; about 20 wt % to about85 wt %; about 25 wt % to about 80 wt %; about 30 wt % to about 75 wt %;about 35 wt % to about 70 wt %; about 40 wt % to about 65 wt %; about 45wt % to about 60 wt %; about 50 wt % to about 55 wt %; about 5 wt %;about 10 wt %; about 15 wt %; about 20 wt %; about 25 wt %; about 30 wt%; about 35 wt %; about 40 wt %; about 45 wt %; about 50 wt %; about 55wt %; about 60 wt %; about 65 wt %; about 70 wt %; about 75 wt %; about80 wt %; about 85 wt %; about 90 wt %; about 95 wt %; or about 99%.

Lubricant Additives

A lubricant fluid of the present invention may optionally include one ormore lubricant additives. Any suitable lubricant additive may be used inthe lubricant fluids of the present invention. In some embodiments, asuitable lubricant additive includes one or more types of carbon chainstructures. Examples of suitable lubricant additives may include but arenot limited to water soluble C₆-C₁₈ phosphoric ester, phosphorous ester,phosphate ester, and organic acid.

In some embodiments, a suitable lubricant additive includes one or morehydrophilic groups. Examples of suitable hydrophilic groups include butare not limited to ethylene oxide, propylene oxide, hydroxyl groups,carboxyl groups, and acyl amine groups.

In some embodiments, a lubricant fluid includes one or more lubricantadditives in an amount of about 0.05 wt % to about 10 wt % of thelubricant fluid; about 0.1 wt % to about 8 wt % of the lubricant fluid;about 0.1 wt % to about 6 wt % of the lubricant fluid; about 0.1 wt % toabout 4 wt % of the lubricant fluid; about 0.1 wt % to about 2 wt % ofthe lubricant fluid; about 0.05 wt % of the lubricant fluid; about 0.1wt % of the lubricant fluid; about 0.5 wt % of the lubricant fluid;about 1 wt % of the lubricant fluid; about 2 wt % of the lubricantfluid; about 3 wt % of the lubricant fluid; about 4 wt % of thelubricant fluid; about 5 wt % of the lubricant fluid; about 6 wt % ofthe lubricant fluid; about 7 wt % of the lubricant fluid; about 8 wt %of the lubricant fluid; about 9 wt % of the lubricant fluid; or about 10wt % of the lubricant fluid.

Functional Additives

A lubricant fluid of the present invention may include one or morefunctional additives. Any suitable functional additive may be includedin the lubricant fluids of some embodiments of the present invention. Insome embodiments, such functional additives may be chosen in order tocover boundary lubrication and other process requirements of aluminumcold rolling. Examples of suitable additives include but are not limitedto anti-rust additives, anti-oxidant additives, pH-adjusting additives,and the like. Any suitable functional additive may be included toachieve the desired result. Examples of a suitable corrosion inhibitoradditive include but are not limited to derivatives of triazole,tolutriazole, organic and inorganic phosphorous compounds, and organicand inorganic phosphate compounds. An example of a suitable antioxidantadditive includes but is not limited to alkylated amino phenol. Anexample of a suitable pH-adjusting additive includes but is not limitedto ammonia, alkane amines, and alkanol amines like trolamine.

In some embodiments, a lubricant fluid includes one or more functionaladditives in an amount of about 0.01 wt % to about 10 wt % of thelubricant fluid; about 0.05 wt % to about 9 wt % of the lubricant fluid;about 0.05 wt % to about 8 wt % of the lubricant fluid; about 0.05 wt %to about 7 wt % of the lubricant fluid; about 0.05 wt % to about 6 wt %of the lubricant fluid; about 0.05 wt % to about 5 wt % of the lubricantfluid; about 0.1 wt % to about 4 wt % of the lubricant fluid; about 0.5wt % to about 3 wt % of the lubricant fluid; about 1 wt % to about 2 wt% of the lubricant fluid; about 0.01 wt % of the lubricant fluid; about0.05 wt % of the lubricant fluid; about 0.1 wt % of the lubricant fluid;about 0.5 wt % of the lubricant fluid; about 1 wt % of the lubricantfluid; about 2 wt % of the lubricant fluid; about 3 wt % of thelubricant fluid; about 4 wt % of the lubricant fluid; about 5 wt % ofthe lubricant fluid; about 6 wt % of the lubricant fluid; about 7 wt %of the lubricant fluid; about 8 wt % of the lubricant fluid; about 9 wt% of the lubricant fluid; or about 10 wt % of the lubricant fluid. Insome embodiments, the lubricant fluid has a pH of about 4.0 to about9.0; about 5.0 to about 8.0; about 6.0 to about 7.0; about 4.0; about5.0; about 6.0; about 7.0; about 8.0 or about 9.0. In some embodiments,a lubricant fluid includes a pH-adjusting additive in an amount suchthat the lubricant fluid has a pH of about 4.0 to about 9.0 at 25° C.

In some embodiments, lubricating fluids of the present invention show,in a typical boundary test on different types of aluminum strips,friction coefficients of about 0.05 to about 0.15; about 0.06 to about0.14; about 0.07 to about 0.13; about 0.08 to about 0.12; about 0.09 toabout 0.11; about 0.05; about 0.06; about 0.07; about 0.08; about 0.09;about 0.10; about 0.11; about 0.12; about 0.13; about 0.14; or about0.15.

In some embodiments, lubricant fluids also include water, such asdemineralized water.

The following examples are provided merely for the purpose of describingsome lubricant compositions representative of the present invention ingreater detail and are in no way to be considered as setting alimitation on the scope of the invention.

EXAMPLES

Single-phase water-based lubricant fluids were evaluated using an arrayof experiments which are considered in the industry to be highlypredictive of the performance of a lubricant package when applied in analuminum cold rolling process, including:

-   -   a) intrinsic lubrication properties evaluated with boundary        lubrication tests;    -   b) thermal stability and evaporation properties with thermo        gravimetric analysis TGA) equipment;    -   c) anti-staining properties with stack staining and energy        dispersive spectrum analysis (EDS) tests; and    -   d) rolling performance characteristics tested with a 2-high        single reversing rolling test mill with a test procedure        correlating to the various production mill processes.    -   Two typical formulations were prepared for use in the examples:

Formulation 1:

EO-PO polymer: 10.0 wt %Phosphoric ester: 1.0 wt %

Trolamine: 0.5 wt %

Demineralized water. 88.5 wt %

Formulation 2:

PEG 200: 90.0 wt %

Phosphoric ester: 1.0 wt %

Tolutriazole: 5.0 wt % Trolamine: 1.5 wt %

Demineralized water: 3.5 wt %

An oil soluble conventional emulsion lubricant package, widely used inmultiple production high speed reversing mills with good performanceresults is a product based on kerosene. This product was used asreference product.

Example 1 Boundary Lubrication

The intrinsic lubrication properties of the lubricant packages wereevaluated in a boundary tester. The applied test procedures are commonlyused for evaluating lubrication properties of lubricants for use inaluminum cold rolling.

Boundary tester T = 60 C. Reference Formulation 1 Formulation 2 SWA1050* CoF** 0.127 0.106 0.098 SWA 3104 CoF 0.081 0.080 0.048 SWA 5052CoF 0.110 0.097 0.051 *SWA 1050/3104/5052: Different aluminum alloys**CoF: coefficient of friction

The reference (usually used in production mills) has coefficients offriction of about 0.08-0.13 on different types of aluminum strips. Asshown in the table above, Formulation 1 demonstrated CoF's successfullywithin this standard range, while Formulation 2 gave lower COF's.

Example 2 Anti Staining Properties

Anti staining properties are key parameters for strip cleanliness afterrolling and annealing. The anti staining properties of the lubricantfluids were evaluated with stack staining tests. This is a key parameterwhich evaluates strip cleanliness after rolling and annealing. To testthe lubricant fluids, the fluid was applied between the surfaces of twoaluminum panels and wrapped tightly with adhesive tapes. The wrappedpanels were then placed in an oven at about 90° C. while pressing with aload of about 4.5 kg. After 24 hours, the wrapped panels were removedand the surfaces observed. Energy dispersive spectrum analysis (EDS) wasapplied to measure amount of different elements on the stained surface.Oxygen was used as subject matter to evaluate the degree ofwater-staining.

O content % Al content % Reference 14.30 85.70 Formulation 1 10.05 89.95Formulation 2 16.52 83.48

The resulting oxygen contents illustrate that the two single-phasewater-based lubricant fluids (Formulations 1-2) exhibit comparable antistaining properties as the traditional products (Reference).

Example 3 TGA

For mills without cleaning line, the evaporation properties of the watersolution lubricant packages are important. In order to be able to rollall aluminum alloys, all materials on the aluminum surface must beremoved below 240° C. Thus, in terms of a TGA curve, products should bevolatilized before this temperature is reached. Thermal stability andevaporation properties of the water solution lubricant packages wereevaluated by thermo gravimetric analysis (“TGA”), to demonstrate thecleanliness of the strip surface after annealing.

The above test results are obtained in air condition. Such testing mayalso be conducted in an oxygen environment.

It can be seen from the results shown in FIG. 1 that the single-phasewater-based lubricant fluids of Formulations 1-2 evaporate at a highertemperature than the reference. However, they are completely evaporatedbelow 240° C. Based on this property, also a clean sheet surface can beexpected after (batch) anneal when using a single-phase water-basedlubricant fluid.

Example 4 Tramp Oil Rejection Property

Tramp oil rejection properties of the lubricant fluids were evaluatedwith anti-tramp oil tests. This is a key parameter which evaluates thesensitivity of the lubricant for pollution. To test the lubricantfluids, 1% tramp oil was mixed in reference and Formulation 1 and 2. Themixtures were then placed in an oven at about 60° C. After 1 hour theamount of tramp oil floating on top of the product was determined

Reference Formulation 1 Formulation 2 1 hour 0% 80% 79% Rejectionpercent

It can be seen from the results shown in table above that thesingle-phase water-based lubricant fluids of Formulations 1-2 exhibitsuperior tramp oil rejection compared to Reference, because in each ofFormulations 1 and 2 about 80% tramp oil has been rejected.

Example 5 Pilot Mill Test

Rolling performances of the water solution lubricant packages wereevaluated by a 2-high single stand reversing rolling test mill fromSouthwest Aluminum Factory. The spraying system is a PE pipe which hasseveral holes on it (range interval 10 cm, bore diameter <2 mm) hungabove the roller (parallel). The liquid flew from a 10 L barrel whichwas positioned higher than the pipe, then went though the pipe anddropped on to the aluminum strip near the entrance side. There was noblown-off at the exit side.

The original thickness of the aluminum strips was 0.57 mm. The stripthickness after rolling one pass with the same force is indicated in thetable.

Thickness after 1 pass Reduction % Reference 0.408 28 Formulation 10.405 29 Formulation 2 0.405 29

The results above demonstrate that aluminum can be rolled withFormulation 1 and 2 and that the exit thicknesses are comparable withthose obtained with the reference. Moreover the surface of the aluminumstrip rolled with the solutions shows a homogeneous metal color which iscomparable with the surface rolled with the reference. The resultsdemonstrate that the surface quality is good.

Example 6 Production Mill Test

Rolling performances of the water solution lubricant packages wereevaluated on a 4-high single stand reversing rolling production mill.The mill width is 1400 mm and work roll's diameter is 300 mm. Themaximum rolling speed is about 4.0 m/s, the maximum rolling force is1000 ton.

Rolling results are below:

Reference:

Entry Exit Roll Thickness Thickness Reduction Width Speed Force mm mm %mm m/s (Ton) Pass 1 4.50 3.10 31% 1000 2.0 450 Pass 2 3.10 2.20 29% 10004.0 500 Pass 3 2.20 1.55 30% 1000 2.0 500

Formulation 1:

Entry Exit Roll Thickness Thickness Reduction Width Speed Force mm mm %mm m/s (Ton) Pass 1 4.50 3.10 31% 1000 2.4 460 Pass 2 3.10 2.20 29% 10004.0 490 Pass 3 2.20 1.55 30% 1000 3.3 480

These results show that aluminum can be rolled under the same conditionswith Formulation 1 as with the reference.

The strip's quality is comparable as rolled with the reference product.No obvious defect on the surface.

Neither Formulation 2 nor an aqueous dilution of it was tested in thismill. Based on the experiments before, it is expected that the rollingperformance will be comparable with Formulation 1.

We claim:
 1. A lubricant fluid for aluminum cold rolling comprising asingle-phase water-based solution, wherein the solution comprises awater soluble polymer.
 2. The lubricant fluid of claim 1, wherein thepolymer comprises at least one hydrophilic group.
 3. The lubricant fluidof claim 2, wherein at least one hydrophilic group comprises ethyleneoxide.
 4. The lubricant fluid of claim 1, wherein the polymer evaporatesat or below 240° C.
 5. The lubricant fluid of claim 1, comprising about10 wt % to about 99 wt % water soluble polymer.
 6. The lubricant fluidof claim 1, wherein the solution further comprises at least onelubricant additive.
 7. The lubricant fluid of claim 6, wherein at leastone lubricant additive is water soluble.
 8. The lubricant fluid of claim6, wherein at least one lubricant additive comprises organic acids ororganic phosphoric ester having a carbon chain of C₆-C₁₈.
 9. Thelubricant fluid of claim 6, comprising about 0.1 wt % to about 10.0 wt %lubricant additive.
 10. The lubricant fluid of claim 1, wherein thesolution further comprises at least one functional additive.
 11. Thelubricant fluid of claim 1, wherein at least one functional additivecomprises anti-rust additives, anti-oxidant additives, pH-adjustingadditives, or combinations thereof.
 12. The lubricant fluid of claim 11,wherein the anti-rust additive comprises inorganic or organic phosphoruscompounds or derivatives of triazole.
 13. The lubricant fluid of claim11, wherein the pH-adjusting additive comprises ammonia, alkane aminesor alkanol amines.
 14. The lubricant fluid of claim 11, wherein thelubricant fluid includes the pH-adjusting additive in an amount suchthat the lubricant fluid has a pH value of about 4.0 to about 9.0 at 25°C.
 15. The lubricant fluid of claim 11, comprising about 0.05 wt % toabout 5.0 wt % functional additive.
 16. A method of cold-rollingaluminum, comprising application the lubricant fluid of claim 1 to analuminum strip.